The present invention generally relates to digital data transmitting systems, and more particularly to a digital data transmitting system for transmitting digital data which are btained by subjecting an information signal to a digital modulation, with a reduced error in the data. The digital data transmitting system according to the present invention is suited in an application where an information signal recording disc having recorded tracks of digital signals is used as a transmitting medium.
Conventionally, when transmitting digital data which are obtained by subjecting an information signal to a digital modulation, an error correcting code is added to and transmitted together with the digital data as is well known. The error correcting code is transmitted so that a code error which occurs during the transmission process can be corrected in a receiver side or a reproducer side, to enable restoration of the correct data.
However, the error correcting code must be subjected to an arithmetic processing in the reproducing system, regardless of whether the error correcting code is a b-adjacent code, a hamming code, or a fire code. Hence, there is a problem in that the reproducing circuit becomes complex and expensive. On the other hand, it is sometimes necessary to selectively transmit digital information signals other than audio and video signals. Such other digital information signals include a control program signal, a graphic information signal (hereinafter simply referred to as a graphic signal), or a character information signal (hereinafter simply referred to as a character signal) to be loaded into a device (a personal computer, for example) which has a discriminating function and is externally coupled to the reproducing apparatus, a musical note signal for causing the personal computer or the like to automatically play music, and a compressed audio signal which is compressed in the time base direction, the bit direction, or both. These other digital information signals will hereinafter be referred to as "information signal data". Conventionally, when transmitting such information signal data, it is only possible to make error corrections with the same probability by use of the error correcting code, although the effects of the errors in the data may be large or small.
An information signal recording disc (hereinafter simply referred to as a disc) may be used as the transmitting path, but a disc itself which is recorded with the information signal data is not in existence. Further, a plurality of kinds of information signal data may be time-sequentially recorded on one track of the disc. However, in this case, there is a problem in that it is impossible to reproduce a desired kind of information signal data from a desired track position, unless an address signal indicative of the kinds of information signal data is recorded on the disc in addition to an address signal indicative of the track position.